TIG remote DIY/ config ideas

[waferhead]

Thanks, I think I found the checkbox I missed in the board config.

[MikeGyver]

I'll make a prototype for my Maxstar 150STH soon.

Let us know results please.

Work on the finger flex remote has begun. Go here http://weldingweb.com/vbb/showthread.php?t=84411

[farmall]

Agree on the "push" sensor. Aircraft use them for good reason due to FEEDBACK (physical resistance) as opposed to mere "position".

Kicka$$ idea, by the way.

[waferhead]

Ended up ordering a pair of the 1/2" round pressure sensors from Sparkfun yesterday.

Used stacked/in parallel they may be directly usable (no active electronics) will add a couple HF filter caps.
Plan is still to put them under the contactor button.

I DO like the idea of the one sensor to do it all, (amps and contactor) but as an electronic tech from way back, I tend to gravitate towards the "boat anchor" level designs if it will do the same job.

(Not that an opamp circuit is complex... It's just that it has more things to go wrong and may need an external shielded box, a tiny card to attach the filter caps etc (and possibly a base current and mode switch) will easily fit in the contactor switch body)

[waferhead]

The sensors arrived already, but it will be tomorrow before I can try it on the Synchro.

Based on what my meter is telling be and the physical sensitivity...

They look plug and play

They go down to >5K with gentle pressure, and <200 ohms with it mashed, but still reasonable pressure I can hold indefinitely, esp mashing on a thumb switch pad.

I'll know pretty quick if it's a suitable substitute or just destined to give me erratic arc current.

[waferhead]

Here's what I had in mind.
I don't have the baseline/gain pot in, but it should have good control range.
I just want to see if this works without driving me crazy... will try this afternoon if my gas bottle delivery guy shows.
Swicth is adjustable for trigger point, it goes on before contact with the gopad.
I have to get some good double sticky tape and connect the cable.
Made the sensor/circuit from some single sided G10 circuit board, 2 filter caps, ground plane on bottom will be at chassis ground to try and keep some the HF put of the sensor lines.

I have a feeling it will be too sensitive to pressure, but that can be fixed electrically or by putting a slight radius on the contact pad.
This is a quick hack to see what I could do with ~$15 and a lunch hour.

[waferhead]

,,,No Argon delivery until Friday.

I'll have to see see if Hodepo will swap a full C25 for Ar... I have a 20cf sitting around I haven't cracked open yet...

[MikeGyver]

Does your welder use a 0-10volt signal? Did you get out output voltage calibrated?

[waferhead]

The synchro has a 15v reference. (open circuit)

The sensor has a max 1mA/sqcm max current density, so I'm at ~50% capacity using it as a direct control as implemented, making some general assumptions about the control circuit. I considered stacking two, but it's pretty sensitive as-is, and I think it has plenty of margin, only one way to know for sure.

The circuit is a simple voltage divider between the reference and a signal gnd, with a tap, just like a footpedal or std hand control pot.
Currently has a 4.7K to ground, and the pressure FSR on the tp leg, open>~200 ohms.
Very simple as implemented, it will get another pot for setting base current and perhaps a mini DPDT switch to reverse operation so pressure lowers current, if only to see how that works.


Still no tech manual, I am about to entirely give up on my LWS, they don't seem remotely interested in ordering anything or even picking up the phone to see how.

[MikeGyver]

If the force sensor is one resistor in the voltage divider, what's the other resistor,a 2nd sensor? If they're in parallel where is your tap/wiper coming from?

[waferhead]

A voltage divider requires two resistors in series, between the reference voltage and gnd ref.
The signal/output tap is in the middle...

I made the top resistor variable, to provide varying amounts of the 15v to get back as the signal.
The opposite would work as well, pulling down the 15v through (for example) a 5K resistor.
...really dead simple...

The only difference between this setup and a potentiometer is that the pot would have a fixed resistance between reference and reference gnd.
In actual operation I don't THINK this will be an issue, as it looks like we are just feeding a voltage follower opamp circuit.

Perhaps I'm missing the question?

[MikeGyver]

So your top resistor is a trimpot... and you're running 2 force sensors in parallel as the bottom resistor?

*EDIT* n/m I see your edit in post #34

[waferhead]

I still need to recheck the reference, I think it changes depending on max setting on the panel on mine.
At 310A on the panel it was 15V.

On a Maxstar the remote may have full control range regardless of panel setting, no idea.

I currently have welder in my sons garage a few miles away, getting at it at all hours is not an option for me.

[waferhead]

The top resistor in the divider is the pressure sensor, but you could think of it as a trimpot electrically.
It changes from essentially open down to ~200 ohms, ~5K-200 ohm at reasonable pressures.

Two force sensors as a divider would be nice but will not work as they both go down...

[MikeGyver]

Ok, I see what u mean.

[waferhead]

Much to my surprise it worked perfect, ran some stick as I won't have argon until tomorrow afternoon.

Tried it with HF cranked all the way up, no weird, had full current control ~5-150A, very easy to control... 150 is all I tried since I only have 3/16" 6013 handy, and I have yet to do the PFC caps and contactor for the limited power feed. (it will do 70A, but 100A+ ain't happenin, needs PFC caps)

Found I could "pulse" it pretty aggressively without imparting any monkey motion, but TIG will be picker than stick I'm sure.

Having pressure controlled variable current on stick feels like cheating...

I need a longer cable, it looks like my TIG torch is 25' instead of 20, the wire I used was kinda stiff telecom cable anyway, need to find something more flexible.

Any suggestions?
I think I have a 25' patch cord somewhere... (Cat5E network cable--- 8 conductor & very flexible)

[farmall]

Copy this thread and any other materials you have to prove you invented this use first.

[waferhead]

I come from a long line of lazy engineers

Actually I just read MikeGyvers idea, and thought about it for 30 seconds, while wiggling my fingers...

I decided the resistive pressure sensor was probably electrically plug and play after looking at the specs, and would work better ergonomically, as I couldn't significantly flex my pinky (or any other fingers) without some slight unintended hand motion.

Building on the good ideas of others is the foundation of innovation. (and all science)
We get pissed when the Chinese do it, but "starting with a man on base" or starting with a working design (even someone elses) is a basic design strategy, and largely how US industry became the huge power it did.

Now we have lawyers...

I have no intention of making these to sell, but after using one for 10 minutes I really wish SSC made them...
It feels like cheating, much more natural than a footpedal.

You could make a really decent one (or design one into a handle) for <$20 easy.
The connector (even the plastic ones) costs more.

A good quality Microswitch for the contactor costs almost as much as the PSR in onesies...

Both pages printed to PDF and saved.

Gregory J. McGee

(I usually go by "piledriver" as my cars are cosmetically challenged, but weldingweb didn't like that nickname)

[Matt_Maguire]

Interesting project waferhead, and RE:

OK, here's the evil plan:
(snip)
OT: Does anyone have a part# for a Tweco#2/4 to Euro adapter? (machine side, gun is Euro)

TA doesn't seem interested in or willing sell me the factory Euro adapter for a 181i in the US, and I won't buy one until I can do it.
It's getting to the point I have contacted places in the UK to buy the "missing" part in US units...

Try http://weldingdirect.com/adkitaircool3.html also ask if you can get the small plastic sleeve instead of that wierd flange cover shown in the picture??? Or you can just use the adapter plug and not use the plastic cover.

Lincoln sells a fast-mate adapter kit for euro torches at about 5 times that money. Abicor-Binzel also sells them.

Good luck
Matt

[waferhead]

Thank you, Matt.

I already have the correct "missing" TA 181i parts coming from England, the Euro adapter itself was 13 Pounds ish, or around $20, also bought the factory inlet an outlets guides with spares.

... shipping cost more than the parts.

Once they arrive I'll order a 181i ;-)

It will probably spend it's life connected to my spoolgun, the 25 feet of freedom would be hard to give up.

[Garauld]

Waferhead - nice project. I've been messin around with a flexiforce pad and remote Parallax stamp microcontroller setup to essentially accomplish the same thing. A mini relay would provide the contact and a digital pot would provide linear feedback based on the flexiforce-sensed pressure. This approach has more customization capability, but definitely costs more than yours.

[waferhead]

Cool, I was thinking that adding lift start to my old Sync would be pretty trivial...
Might come in handy working on cars, saves pulling the computer etc.

Linearity doesn't seem to be an issue, the effective range on this is ~10K-200 ohms, it's very linear in that range.
There's a step function at the top end,(100K or so) but that's like a gerbil blowing at it through a straw.

It just occurred to me that I can make a pedal with this same setup.
It can be installed (and used) in parallel, as the PSR and contactor switch are effectively open when not in use.
Getting the force right might take a little experimentation on the pedal implementation.

That way you could use the handheld for primary current and tap along with Metallica with your foot for pulse. >:-)

[Warpspeed]

The usual reason for using a two watt pot is because just about all two watt pots are wire wound not carbon track type.

There are three classes of potentiometer which are mostly selected for their mechanical, wear, and reliability properties.

Carbon track type are ideal where the setting is very rarely changed, such as the brightness and contrast control on your TV. They are very cheap, and wear out quickly, or become noisy or intermittent with age or constant use.

Wire wound type are far more robust and reliable, with fairly constant use, but they are a bit larger and cost a bit more. A very good choice for a welder that sees constant heavy use, and is constantly being tweaked for different jobs.
More often than not they are selected for suitability rather than actual power dissipation.
Something much smaller will often work fine, for a while.

Plastic track pots are for extreme constant motion applications, such as position indication on a continuously moving robot arm. They are usually rather large very solidly built, and fitted with ball bearings, and the high price may really surprise you.

[waferhead]

I melted some metal for about an hour today just to get some seat time and try out the PSR hand control setup.

Let's just say I no longer have any desire for a foot pedal, and if someone gave me one I would be ripping it apart to figure out how best to install the PSR setup for foot control.

The setup needs integrated into the handle, and preferably set up so it could be used from any angle...

... but you'll have to pry it from my cold, dead hands.

Tried rapid pulsing with it, got some side to side monkey motion, but it actually worked quite well, and sometimes a little side to side is what you want.

I was able to use the lay wire technique and still make it look like I gave a damn.

Diggin 330cf bottle at ~2600PSI, I think it went up...

[waferhead]

Already working on V2 to eliminate the dependance on the cheap $3 Chinese switch body and make it robust.

Trying to track down a matching round membrane switch to sandwich together with the PSR, whole shebang will go in a sealed flat rubber dongle that can stick to any flat spot, simple to make a light tubular slip on /rotatable handle for a TIG torch with a recessed flat spot... will be dustproof/waterproof and reasonably tough, possibly even welder resistant ;-)

Will try just using a sealed 6 or 8 pin phone jack, trivial plug in and flexi cables available cheap.